Curing and polymerizing processes employing beta-substituted diperoxyketals

ABSTRACT

IMPROVEMENTS IN THE POLYMERZATION OF ETHYLENICALLY UNSATURATED MONOMERS, THE CURING OF UNSATURATED HPOLYESTER RESIN COMPOSITIONS, AND THE CURING (PREFERABLY CURING AND FOAMING) OF ELASTOMER COMPOSITIONS ARE ACHIEVED BY THE USE OF CERTAIN B-SUBSTITUTED DIPEROXYKETALS OF THE FORMULA   R3-C(-R2)(-R4)-C(-R5)(-R6)-C(-O-O-R1)2-R   SUCH AS 2,2 - DI(T - BUTYLPEROXY) - 4 - METHYLPENTANE AND 4,4-DI(T-BUTYLPEROXY) HEPTANE.

United States Patent Oflice' ,Patented Aug. 27, 1974 ABSTRACT OF THEDISCLOSURE Improvements in the polymerization of ethylenicallyunsaturated monomers, the curing of unsaturated polyester resincompositions, and the curing (preferably curing and foaming) ofelastomer compositions are achieved by the use of certain ,B-substituteddiperoxyketals of the formula such as 2,2 di(t butylperoxy) 4methylpentane and 4,4-di(t-butylperoxy)heptane.

This is a division of application Ser. No. 43,208, filed June 3, 1970(now US. Pat. No. 3,686,102, issued Aug. 22, 1972).

BACKGROUND OF THE INVENTION (a) Field of Invention This inventionrelates to improved processes for polymerizing ethylenically unsaturatedmonomers, curing unsaturated polyester resins, and curing elastomercompositions by employing as catalysts certain [El-substituteddiperoxyketals.

(b) Related Art Diperoxyketals as a class of peroxides have about ten- 7hour half-lives at about 90-120 C. With such charac teristics, their usehas been disclosed for curing of unsaturated polyester resins, forpolymerizing ethylene and other vinyl monomers, and for crosslinking (orcuring) of natural and synthetic rubbers and ethylene homo andcopolymers. They have also found uses as additives in diesel fuel and asfree-radical generators in the synthesis of organic compounds.

Since diperoxyketals are normally prepared from lowcost ketones andlow-cost hydroperoxides (usually t-butyl hydroperoxide--t indicatingtertiary), they are potentially low-cost sources of free-radicals.Currently marketed are three such derived diperoxyketals, i.e., 2,2-di(tbutylperoxy)butane; 1,1 di(t butylperoxy) 3,3,5-

trimethylcyclohexane; and n-butyl 4,4 di(t butylperoxy) valerate. Thethird of these has a much longer half-life and is thus of more limiteduse in curing of unsaturated polyester resins and in initiating vinylpolymerizations.

Dickey (US. Pat. No. 2,455,569) is the initial patent disclosing a widerange of diperoxyketals and diperoxyacetals. While not giving examples,Dickey disclosed that, on the basis of the properties possessed by theseperoxidic compounds, they may be useful as diesel fuel additives,polymerization initiators, curing agents for polyester resins, etc.However, no attempt is made in the patent to differentiate among whichof the compounds might be more useful for a given application, etc.

Several patents have subsequently issued disclosing that specific typesof diperoxyketals are more useful in certain applications. For example,US. Pat. No. 2,650,913 discloses the use of 2,2-di(t-butylperoxy)butaneat a catalyst for ethylene polymerization; US. Patents 2,656,- 334 and2,692,260 disclose vinyl polymerizations employing catalyst combinationssuch as dibenzoyl peroxide and 2,2 di(t butylperoxy)butane; Netherlandsapplication 6,403,775 (Ian. 25, 1965) discloses high pressure ethylenepolymerization using various di(t-butylperoxy) ketals derived fromcyclohexanone and substituted cyclohexanones; US. Pat. No. 2,698,311discloses the curing of unsaturated polyester resins such as diallylphthalate/ polyethylene glycolfumaratc using 2,2-di(t-butylperoxy)butaneas a curing agent (or catalyst); German Pat. No. 945,187 discloses theuse of 2,2 di(t butylperoxy)butane and 1,1 di(tbutylperoxy) 3,3,5trimethylcyclohexane as catalysts for a rubber vulcanizing process.Similar disclosures are also found in US. Pats. 3,344,125 and 3,296,184.

BRIEF SUMMARY OF THE INVENTION This invention concerns improvedprocesses for:

(A) Polymerizing ethylenically unsaturated monomers which are responsiveat suitable temperatures and pressures to initiating amounts of freeradical generators as polymerization initiators;

(B) Curing unsaturated polyester resin compositions by heating in thepresence of initiating amounts of free radical polymerizationinitiators; and

(C) Preparing foamed, cured elastomers by heating a compositioncontaining elastomer, blowing agent and freeradical generating curingagent in the absence or presence of fillers and additives, theimprovement residing in the use, as said initiator or curing agent, abeta (,B)-substituted diperoxyketal of the formula 4 R5 (BOR where R isa lower alkyl radical or can be equivalent to -C-CRa;

R is a t-alkyl or t-cycloalkyl radical having 4-7 carbon atoms, at-aralkyl radical having 9-20 carbon atoms, or both R s taken togethercan form an alkylene diradical of 6-12 carbon atoms having atert.-carbon atom at each end;

R and R are selected from H or lower alkyl, cycloalkyl, lower alkoxy,cycloalkoxy, phenoxy or substituted phenoxy, aralkoxy, acyloxy andaroyloxy radicals and can be the same or ditferent except that only oneof R and R, can be H;

R, is selected from H, when R is other than methyl, or a lower alkyl,cycloalkyl, lo'wer alkoxy, cycloalkoxy, phenoxy or substituted phenoxy,aralkoxy, acyloxy or aroyloxy radical; and

R and R, can be the same or different and are selected from H and loweralkyl.

For the above defined R groups, the lower alkyl and alkoxy radicalsnormally contain 1-4 carbons; the cycloalkyl and cycloalkoxy radicals,3-7 carbons; the aralkoxy radical, 7-16 carbons; the acyloxy radical,1-4 carbons; and the aroyloxy radical, 6-12 carbons.

DETAILED DESCRIPTION OF INVENTION It has now been discovered that higherpolymerization efliciencies, faster curing of unsaturated polyesterresin compositions, and foamed, cured elastomers with superior densityand ultimate tensile values are obtained when the above-definedfl-substituted diperoxyketals are employed than when employing otherdiperoxyketals or other leading commercial peroxides such as dibenzoylperoxide).

Diperoxyketals prepared by methods well-known to the art and arenormally derived from B-substituted acyclic ketones. The following listof diperoxyketals are typical examples of those defined by the formulawhich are useful in the practice of this invention:

2,2-di(t-butylperoxy)-4-methylpentane,2,2-di(t-butylperoxy)-3,4-dimethylpentane,2,2-di(t-butylperoxy)-3,3,4-trimethylpentane,2,2-di(t-butylperoxy)4-cyclohexyl-4-methylpentane, 2,2-di(t-butylperoxy) -4- cyclohexyloxy-4-methylpentane,2,2-di(t-amylperoxy)4-methylpentane,2,2-di(a-cumylperoxy)4-methylpentane, 3,3-di(t-butylperoxy5-methylheptane, '3,3-di-t-amylperoxy)-S-methylheptane,3,3-di(a-cumylperoxy)-5-methylheptane,

2,2-di t-butylperoxy) 4-methoxy-4-methylpentane,

' 2,2-di (t-amylperoxy -4 methoxy-4-methylpentane,

2,2-di(a-cumylperoxy)-4methoxy-4-methylpentane,4,4-di(t-butylperoxy)-2,6-dimethylheptane,4,4-di(t-amylperoxy)-2,6-dimethylheptane,4,4-di(a-cumylperoxy)-2,6-dimethylheptane, 2,2-di(t-butylperoxy-4,4-dimethylpentane, 2,2-di(t-amylperoxy)-4,4dimethylpentane, 2,2-dia-cumylperoxy -4,4-dimethylpentane, 3,3-di(t-butylperoxy)hexane,3,3-di(t-amylperoxy)hexane, 3,3-di(a-cumylperoxy)hexane,3,3-di(t-butylperoxy)heptane, 3,3-di(t-amylperoxy)heptane,3,3-di(a-cumylperoxy)heptane, 4,4-di(t-butylperoxy)heptane,4,4-di(t-amylperoxy)heptane, 4,4-di(a-cumylperoxy)heptane, 2,2-di(t-butylperoxy) 4 methyl-4-phenoxypentane,2,2-di(t-amylperoxy)-4-methyl-4-phenoxypentane, 2,2-di a-cumylperoxy4-methyl-4-phenoxypentane,2,2-di(t-butylperoxy)-4-acetoxy-4-methylpentane,2,2-di(t-amylperoxy)4-acetoxy-4-methylpentane, 2,2-di a-cumylperoxy4-acetoxy-4-methylpentane,2,2-di(t-butylperoxy)-4-benzoyloxy-4-methylpentane,2,2-di(t-amylperoxy)-4-benzoyloxy-4-methylpentane,2,2-di(a-cumylperoxy)-4-benzoyloxy-4-methylpentane,4,4-di(t-butylperoxy)-2,6-dimethoxy-2,6-dimethylheptane,4,4-di(t-amylperoxy)2,6dimethoxy-2,6-dimethylheptane,3-isobutyl-3,6,6,9,9-pentamethyl-l,2,4,5-tetraoxacyclononane,3-neopentyl-3,6,6,9,9-pentamethyl-l,2,4,5-tetraoxacyclononane,3,6,6,9,9-pentamethyl-3-(2-methoxy-2'-methylpropyl)-1,2,4,S-tetraoxacyclononane,3-(2'-methylbutyl)3-ethyl-6-6,9,9-tetramethyl-1,2,4,5-

tetraoxacyclononane,3butyl-3ethyl-6,6,9,9-tetramethyl-l,2,4,5-tetraoxacyclononane,6,6,9,9-tetramethyl-3,3,di-n-propyl-1,2,4,5-tetraoxacyclononane,3,3diisobutyl-6,6,9,9-tetramethyl-1,'2,4,5-tetraoxacyclononane and I3-isobutyl-3,6,6,l 1,1l-pentamethyl-l,2,4,5-tetraoxacycloundecane.

Preferred diperoxyketals include 2,2-di(t-butylperoxy)4-methylpentane,2,2-di(t-amylperoxy)-4-methylpentane,2,2-d1(t-butylperoxy)-4methoxy-4-methylpentane,

3,3-di(t-butylperoxy)5-methy1heptane, 3,3-di(t-butylperoxy)heptane,4,4-di(t-butylperoxy)-2,6-dimethylheptane and 4,4-di (t-butylperoxy)heptane.

Polymerization In the free-radical initiated polymerization orcopolymerization of ethylenically unsaturated monomers at suitabletemperatures (and pressures), the subject diperoxyketals are found toprovide improved efficiencies on a kinetic basis (efiiciency ofinitiator to generate radicals useful for initiating polymerizations) aswell as on weight and equivalent bases.

Ethylenically unsaturated monomers include olefins such as ethylene,propylene, styrene, vinyl toluene, vinyl pyridine divinyl benzene,alpha-methylstyrene, 1,3-butadiene, isoprene and chloroprene: vinylesters such as vinyl acetate, vinyl propionate, vinyl laurate, vinylbenzoate and divinyl carbonate: unsaturated nitriles such asacrylonitrile and methacrylonitrile: acrylic acid and methacrylic acidand their esters and amides such as methyl, ethyl, n-butyl and2-ethylhexyl acrylates and methacrylates and acrylamide andmethacrylamide; maleic anhydride; maleic acid and fumaric acid and theiresters; vinyl halo and vinylidene dihalo compounds such as vinylchloride, vinyl fluoride, vinyl bromide, vinylidene chloride andvinylidene fluoride; perhalo olefins such as tetrafluoroethylene,hexafluoropropylene and chlorotrifluoroethylene; vinyl ethers such asmethyl vinyl ether and n-butyl vinyl ether; acrolein; and mixturesthereof. Preferred (co) polymerizable monomers includes styrene andvinyl acetate.

Temperatures of about 20-300 C. and diperoxyketal levels of about 0.01%to 5% or more by weight, based on the monomer, are normally employed inthe polymerizations. Conventional solvents may optionally be added(e.g., benzene) to the reaction system.

While most vinyl polymerizations are performed at atmospheric pressure,there appears to be a need in the polyethylene industry for an initiatorto be used at pressures up to 4000 atmospheres and in the ISO-300 C.temperature range for the preparation of low density polyethylene.Dialkyl peroxides and t-butyl peroxybenzoate decompose to initiatorradicals too slowly whereas diacyl peroxides decompose too rapidly toinitiator-radicals to be of use. On the other hand diperoxyketalsdecompose at about the proper rate to be useful in this respect. Use of2,2-di(t-butylperoxy)butane (normally a liquid) in high pressureethylene polymerizations is not ideal since at the high pressuresemployed it solidifies either in the pure form or in an ethylene or ahydrocarbon solution and cannot be pumped and metered into thepolymerization reactors at certain desired concentrations. Itssolubility at high pressures is improved somewhat by use of more polarsolvents such as methanol. However, traces of these solvents get trappedin the polymer thus limiting the utility of the resulting polyethyleneresin. Hence there is a need for an efficient diperoxyketal which willremain as a liquid at the pressures employed in ethylenepolymerizations, either in the pure form or as a solution in ethylene orin a hydrocarbon solvent. A test that stimulates the effect of highpressures on the solidification of pure peroxides or solutions of theperoxides is described as follows: The diperoxyketal is dissolved in ahydrocarbon solvent to give a 50% solution by weight. The solution isthen cooled to 30 C. and the state of matter is noted. Then the solutionis cooled to 78 C. and the state of matter is again noted. When thesetests are applied to three diperoxyketals of this invention(2,2-di(t-butylperoxy)-4- methylpentane, 3,3-di(t--butylperoxy)heptaneand 3,3-di '(t-butylperoxy)5-methylheptane) and some conventionaldiperoxyketals (2,2-di(t-butylperoxy)butane and 1,1-di(t-butylperoxy)cyclohexane), the diperoxyketals of this invention passthe tests whereas the others fail.

Curing of polyester resins In curing unsaturated polyester resincompositions by heating at suitable curing temperatures in the presenceof free radical polymerization initiators, the use of diperoxyketals ofthis invention are found to give faster cures (that is, are most active)than conventionally used diperoxyketals and peroxidic compounds.

Unsaturated polyesters which are used as the one component of thepolyester resin compositions according to the present invention are, forinstance, polyesters as they are obtained by esterifying preferablyethylenically unsaturated dior polycarboxylic acid or their anhydrides,such as maleic acid, fumarie acid, glutaconic acid, itaconic acid,mesaconic acid, citraconic acid, allyl malonic acid, allyl succinicacid, and others, with saturated or unsaturated polyalcohols such asethylene glycol; diethylene glycol (2,2,dihydroxy ethyl ether);triethylene glycol (ethylene glycol bis(Z-hydroxy ethyl ether);propanediol- 1,2; butauediol-1,3; 2,2-dimethyl propanediol-l,3; butene(2)-diol-1,4, glycerol, pentaerythritol, mannitol, and others. Mixturesof such acids and/or alcohols may also be used. The unsaturated diorpolycarboxylic acids may be replaced, at least partly, by saturatedcarboxylic acids such as adipic acid, succinic acid, sebacic acid, andothers, or by aromatic dicarboxylic acids, such as phthalic acid,tetrahydrophthalic acid, and others and their anhydrides such asphthalic anhydride. The acids used as well as the alcohols employed maybe subsititued by other substituents, preferably by halogen. Examples ofsuitable halogenated acids are, for instance, trtrachloro phthalic acid;1,4,5,6,7,7-hexachloro hicyclo "2 2,1) heptene (5)-2,3-dicarboxylicacid, and others, or their anhydrides.

The other component of the unsaturated polyester resin compositions areunsaturated monomers, preferably ethylenically unsaturated monomers suchas styrene, vinyl toluene, methyl methacrylate, diallyl phthalate,dibutyl fumarate, 'acrylonitrile, triallyl cyanurate, a-methyl styrene,divinyl benzene, methyl acrylate, diallyl maleate, n-butyl methacrylate,ethyl acrylate, and others, which are copolymerizable with saidpolyesters.

A preferred resin composition contains as the polyester component theesterification product of propylene glycol (a polyalcohol), maleicanhydride (anhydride of an unsaturated dicarboxylic acid) and phthalicanhydride (anhydride of an aromatic dicarboxylic acid) and as themonomer component styrene.

Temperatures of about 20200 C. and diperoxyketal levels of about 0.05%to 5% or more by weight of curable unsaturated polyester resin arenormally employed.

Other important features of the invention diperoxyketals, compared tosome conventional peroxides used in polyester curing, are that they areliquids which can be more readily mixed with the resins that availablesolid peroxides or special solid peroxide solutions and that they arethermally stable at ambient temperatures, thus not requiringrefrigerated storage and shipment.

Curing of elastomers The diperoxyketals of this invention are alsouseful for curing (crosslinking or vulcanization) or curing and foamingof elastomers such as ethylene-propylene co polymers and terpolymers,polyethylene, ethylene-vinyl acetate copolymers, silicon rubbers,styrene-butadiene rubbers and the like in the presence or absence ofadditives and fillers such as sulfur, carbon black, silica, clay,carbonates, antioxidants, heat and light stabilizers, dyes,accelerators, zinc oxide, oils, etc.

An especially useful application for the invention diperoxyketals is asa curing agent in the preparation of foamed, cured elastomercompositions (particularly ethylene-propylene coand ter-polymers) byheating at suitable temperatures an intimately dispersed mixture ofelastomer, blowing agent, free radical generating curing agent and,optionally, additives and/or fillers. The temperature range is usuallyabout 240450 F., preferably 280375 F. The diperoxyketal level isnormally about 0.1-l0.0 phr. (parts per hundred of resin), prefera'bly0.1-5. The blowing agent is usually used in an amount of about 05-10phr. and the amount of filler may vary from about 0 to phr.

Any of the well-known chemical blowing agents can be used in thepreparation of the foamed articles in accordance with this invention as,for example, azobisformamide, diazoaminobenzene,N,N-dinitrosopentamethylene tetramine,N,N'-dimethyl-N,N'-dinitrosoterephthalamide, p,p'- oxy bis(benzenesulfonyl semicarbazide), azobis(isobutyronitrile), p,p-oxybis-(benzenesulfonyl hydrazide), p, p-diphenyl-bis(sulfonyl hydrazide), benzenesulfonyl hydrazide and m-benzene-bis-(sulfonyl hydrazide). Any of thewell-known solvent blowing agents may also be used in this invention,as, for example, methyl chloride, methylene chloride,monochlorotrifluoromethane, monochlorodifluoromethane, 1,2-dichlorotetrafiuoroethane, 1,1,2- trichloroethane, chloroform, carbontetrachloride, and low boiling hydrocarbons such as butane, pentane andhexane. Accordingly, any compound which decomposes or volatilizes toyield at least one mole of gas per mole of blowing agent at atemperature of C. or less may be used. When preparing foamed elastomersit is essential that the foaming occurs at the proper viscosity of theelastomer just prior to the curing. Once the elastomer is cured, itbecomes crosslinked and cannot be foamed. Thus, if the curing agentdecomposes too fast, the elastomer cannot be formed.

Also, if the curing agent decomposes too slow, or if higher temperaturesare required, then the gases released from the blowing agent escape fromthe elastomer due to a time factor or to the lower than ideal viscosityat the higher temperatures used. The curing agent also should not be toovolatile where it can be lost due to evaporation before the curingtemperature is reached.

The diperoxyketals of this invention are ideally suited as curing agentswhen certain elastomers such as the ethylene propylene copolymers andter-polymers are foamed. This is illustrated in Examples V and VI.

Conventional diperoxyketals have certain drawbacks in this application.N-Butyl 4,4-di(t-butylperoxy)valerate decomposes at too high of atemperature; the cyclic perketals such as 1,1di(t-buty1peroxy)cyclohexane and 1, 1 di(t-butylperoxy) 3,3,5trimethylcyclohexane decompose at too low temperatures; and2,2-di(t-butylperoxy)butane is somewhat too volatile.

In mold curing and foaming, the diperoxyketals of this invention haveother advantages over the higher temperature prior art curing agentssuch as n-butyl 4,4-di(tbutylperoxy)valerate. Because of the lowercuring temperatures that can be used with our products, i.e. below 320F., the molds can be opened immediately after the curing is finished.When n-butyl 4,4-di(t-butylperoxy) valerate is used, the mold has to becooled down before the mold is opened. This is undesirable in productiondue to the extra time and cooling involved which is costly. It is alsoessential in mold curing that the curing agent does not decompose andcure the resin prior to the decomposition of the blowing agent. Thus,the low temperature curing agents as discussed above are alsoundesirable in this application as well as in the atmospheric foamingand curing applications.

EXAMPLES The following examples illustrate the subject invention and arenot in limitation thereof.

The first two examples illustrate the curing of unsaturated polyesterresins. Given below are the description of the polyester resincomposition and curing procedure used in Examples I and II:

Basic Unsaturated Polyester Resin.The composition of the unsaturatedpolyester resin had the following composition:

dustry standard in polyester curing). A second standard at an equalactive oxygen level was t-butyl peroxybenzoate. These data aresummarized in Table I. Using cure times as a criterion for activity, thedata show that in general the diperoxyketals of this invention (Nos. 1

component 5 through 7) have significantly greater activity than con-Maleic'anhydride moles 1 ventional diperoxyketals (Nos. 8 through 12)and t-butyl Phthalic anhydridg do peroxybenzoate (No. 13) at equalweight as Well as at Propylene glycol equal active oxygen levels. Inaddition, at equal active Acid No alkyd g u oxygen levels several of thediperoxyketals of this inven- ""7"" tion (Nos. 2, 3, 4 and 6) are fasterthan dibenzoyl perox- Inhlbltor added (Hydroqumone) "percent" ide (No.14) and at 1% weight levels almost all of the di- Seven (7) parts byweight of the above alkyd resin peroXyketals Of this invention 1, 2, 6and was diluted with three (3) parts by weight of monomeric are fasterthan dibenzoyl peroxide (No. 14).

TABLE I 100 0. 212 F.) SPI exoterms Active oxygen level equal to 1%dibenzoyl peroxide 1% peroxide level Peak Barcol Peak Barcol Gel, Cure,exothenn, hard- Gel, Cure, exotherm, hard- Number Peroxide min H1111. F.ness mm. min. F. ness 1 2,2-di-(t-butylperoxy) -4-methylpentane 2. 2 3.3 430 40-45 1. 3 2. 1 432 40-45 22,2-di-(t-butylperoxy)-4-methoxy-4-methy1pentane 1. 0 1. 7 422 40 0.6 1. 2 420 45 3 ,3-di(t-butylperoxy)-5-methylheptane 1. 5 3 4 7 40 1.1 1. 8 426 35 4 2,2-dit-butylperoxy)'4,4-dimethylpentane 0. 5 1. 1 41040 0. 3 1. 1 390 45 5 3,3-di-(t-butylperoxy)-heptane 3.0 4. 1 426 35 2.2 3.2 430 40 6- 4,4-di-(t-butylperox y) -2,6-dimethy1heptane 1. 8 2. 7426 40 1. 5 2. 4 425 35-40 7 2,2-di-( -amylperoxy)-4-methylpentane. 33-3 4 45 2. 0 3. 0 426 45 8 2,2-di-(t-butylperoxy) 5-methylhexane 3. 54. 9 424 40 2. 6 3. 6 432 35 9- 2,2-di-(t-butylperoxy)-pentane 3. 9 5. 4421 30-30 2. 6 3. 8 432 30 10.. 2,2-di-(t-butylper0xy)-butane1 4. 7 6. 5416 40 3. 7 4. 9 433 40-45 111,1-di-(t-butylperoxy)-3,3,5-trimetliyleyclohexan 3. 0 4. 1 419 40 2. 83. 8 432 45 12 1,1-di-(t-butylperoxy)-cyclohexane 5. 3 7- 1 4 6 35-40 4.4 5. 7 429 35-40 13 t-Butylperoxybenzoate 11.8 14.3 414 35-40 14Dibenzoyl peroxide 2.0 3.1 424 45 2.0 3.1 424 45 styrene. The resultingunsaturated polyester resin had the following physical properties:

(a) Viscosity (Brookfield No. 2 at r.p.m.) poises 13.08 (b) SpecificGravity 1.14

Example I.SPI Exotherm Data on Diperoxyketals, Di-

benzoyl Peroxide and t-Butyl Peroxybenzoate at 100 C. (212 F.)

Using the Standard SPI Exotherm procedure at 100 C. (212 F), variousdiperoxyketals were employed as curing catalysts at equal active oxygenlevels and equal weight levels compared to 1% by weight of unsaturatedpolyester resin of dibenzoyl peroxide (a well known in- Example ILAPIExotherm Data on Diperoxyketals and Dibenzoyl Peroxide at 82 C. (180 F.)

As in Example I, various diperoxyketals were compared to 1% dibenzoylperoxide (No. 12) in the basic unsaturated polyester resin at equalactive oxygen and 1% Weight levels employing the Standard SPI Exothermprocedure at 82 C. 180 F). These data are summarized in Table II. Again,the diperoxyketals of this invention (Nos. 1 through 7) are faster thanconventional diperoxyketals (Nos. 8 through 11). At an equal activeoxygen basis several of the diperoxyketals of this invention (Nos. 2, 3,4 and 6) are faster than dibenzoyl peroxide and at 1% weight levelsalmost all of the diperoxyketals of this invention (Nos. 1, 2, 3, 4, and6) are faster than dibenzoyl peroxide.

The results from Examples I and II demonstrate that the diperoxyketalsof this invention are significantly superior to conventionaldiperoxyketals in curing unsaturated polyester resins. In addition, thediperoxyketals of this invention have activities in unsaturatedpolyester resins similar to and in some cases higher than dibenzoylperoxide, a long time standard in the industry.

TABLE II 82 0. (180 F.) SPI exotherms Active oxygen level equal to 1%dibenzoyl peroxide 1% peroxide level Peak Barcol Peak Barcol Gel, Cure,exotherm, hard- Gel, Cure, exotherm, hard- Number Peroxide min. min. Fness min. min. F ness 1 2, 2-di-(t-butylp eroxy) -4-meth ylpentane 4. 16. 2 385 -30 2. 7 4. 2 400 40 2 2,2-di-(t-butylperoxy)-4-methoxy-4methylpentane 1. 4 2. 5 380 40 0. 7 l. 9378 3, 3-di-(t-butylperoxy)-5-methylheptane 2. 5 3. 9 394 30 1. 7 2. 7397 -40 2, Z-di-(t-butylperoxy) -4, 4-dimethylpentane. 1. 2 2. 2 392 0.9 1. 5 403 3, 3-di-(t-butylperoxy)-heptane 4. 6 7. 3 388 25 3. 4 5. 2401 35 4, 4-di-(t-butylperoxy)-2, fi-dirnethylheptan 2. 7 4. 3 396 30-352. 1 3. 3 404 35-40 2, 2-di-(t-amylperoxy)4-methylpentane 5. 5 8. 2 38125 4. 0 6. 2 398 4 2, 2-di-(t-buty1peroxy)-5-methylhexane 9. 2 12. 9 36135 6. 0 9. 1 378 2, 2-di-(t-butylperoxy) -pentane 9. 6 13. 9 352 30 5. 68. 3 382 35 2, 2 di-(t-butylperox y) -butane 12. 8 17. 1 352 35 7. 7 10.9 378 40 1, 1-di-(t-buty1peroxy)-3, 3, S-trimethylcyelohexane. 6.0 8.9377 40 4. 5 6. 7 392 40 12 Dibenzoyl peroxide 3. 2 4. 7 394 45 3. 2 4. 7394 40 Example IIL-High Conversion Styrene Polymerization Efficienciesof Diperoxyketals Compared to those of t-Butyl Peroxybenzoate Theefiiciencies of several diperoxyketals as free-radical initiators forstyrene bulk polymerizations at 100 C. compared to those of t-butylperoxybenzoate, a well known and efiicient art peroxide, weredetermined. The following procedure was employed:

A series of Pyrex tubes was filled with styrene solutions containingvarying amounts of free radical initiator, several tubes being used foreach initiator. The amounts of free-radical initiator in the tubes wereadjusted so that the resulting conversion versus concentration plotswould cross 98.5 conversion, ideally, after 8.5 hours at 100 C. 98.5conversion was selected since styrene polymerizations are carried outalmost to complete conversion commercially. Hence initiators thatdead-end after 90% conversion and before 98.5% conversion or achieve98.5 conversion after using very large quantities of initiator are notattractive commercially. After fusing out with N gas the tubes weresealed and placed in a constant temperature bath thermostatted at 100C..After 8.5 hours at 100 C. the tubes were removed and quickly chilledto C. to prevent post polymerization. The sealed tubes were then brokenand the polymer was taken up in 100 ml. of benzene. The resultingsolution was poured into 1000 ml. of methanol to precipitate the poly(styrene) and the polymer was separated by filtration and was dried in anoven at 50-55 C. The conversion of styrene to polymer was thendetermined and plots of initiator con- 10 peroxybenzoate F /F wouldequal 1.0. Although the F F values of the diperoxyketals of thisinvention (Nos. 1 and 2) are somewhat less than 1.0 they aresignificantly higher than those of the art diperoxyketals (Nos. 4, 5, 6and 7) and that of a diperoxyketal (No. 3) from a dissimilarlysubstituted ketone. Other diperoxyketals of this invention, such as Nos.8 and 9, have F /F values greater than 1.0. In the cases of wt. /wt. andeq. /eq. values the lower these ratios are than 1.0 the more efiicientand attractive the initiator. When these values are less than 1.0 theinitiator is more efiicient on a weight and/or equivalent basis thant-butyl peroxybenzoate. The diperoxyketals of this invention (Nos. 1, 2,8 and 9) have lower values of wt. /wt. and eq. /eq. than a diperoxyketalrom a gamma substituted ketone (No. 3) and the art diperoxyketals (Nos.4, 5, 6 and 7) [even though 1,1-di-(tbutylperoxy) 3,3,5trimethylcyclohexane (No. 5) and l,l-di-(t-butylperoxy)cyclohexane (No.6) have significantly lower half-lives than the diperoxyketals of thisinvention (lower half-lives of initiators decrease wt. wt. and eq. /eq.values) The diperoxyketals of this invention (Nos. 1, 2, 8 and 9) arevery much more etficient than t-butyl peroxybenzoate at 100 C. for 8.5hours in styrene on weight and equivalent bases.

Hence, in the polymerization of vinyl monomers such as styrene, thediperoxyketals of this invention are more efficient than the artdiperoxyketals and diperoxyketals from unsubstituted acyclic ketones,dissimilarly substituted acyclic ketones and substituted andunsubstituted cyclic ketones.

TABLE III 100 C. styrene polymerization efirciencies of diperoxyketalscompared to t-butyl peroxybenzoate 100 C. Styrene elfieiency benzeneConver- I hall-life, sion, Eq. Number Peroxide hrs. percent FilFzWt.1/wt.z eq.:

1 2,2-di-(t-buty1peroxy)4-methy1pentane 10. 6 98.5 0.71 0.56 0.83 23,3-di-(t-butylperoxy)heptane 9.7 98.5 0.91 0.42 0.59 32,2di-(t-buty1peroxy)5-methylhexane 21. 5 98.5 0.57 1.48 2.08 4.-.2,2-di-(t-butylperoxy)butane 10.2 "98.0 0.19 1.81 2.99 51,1-di(t-butylperoxy)3,3,5-trimethy1eyclohexane. 3. 8 98. 5 0. 24 0. 720. 92 6. 1,1-di-(t-buty1peroxy)cyelohexane 4. 4 98. 5 0.22 0. 74 1. 117. 3,3-di-(t-butylperoxy)pentane... 13.0 98.0 0.56 0.82 1.284,4-(11-(t-butylperoxy)-heptane. 10.0 98.5 1.01 0.39 0.552,2-di-(t-amylperoxy)4-rnethy1pentane- 11.5 98.5 1. 41 0.50 0.67

*Maximum conversion that could be obtained with these initiators.

centration versus conversion were constructed. The initia torconcentration required to attain 98.5% conversion (or thereabout) wascompared, under similar conditions, to that of t-butyl peroxybenzoate.Equation (1) was used to determine efficiency data.

F /F is the efficiency of the initiator under investigation compared tothat of t-butyl peroxybenzoate (F Rp and Rp are rates of polymerizationof initiator and t-butyl peroxybenzoate, respectively, Kd and Kd aredecomposition rate constants for initiator and t-butyl peroxybenzoate,respectively, and [I], and [I1 are concentrations of initiator andt-butyl peroxybenzoate, respectively, required for attainment of 98.5%conversion after 8.5 hours at 100 C. Under these conditions:

We also know Kd /Kd from the half-lives of t-butyl peroxybenzoate andinitiator, respectively. Hence we can calculate F /F values for eachdiperoxyketal initiator. These data are shown in Table III. Alsoincluded in Table III are wt. /wt. and eq. /eq. values which representratios of weights and equivalents, respectively, of initiator to tbutylperoxybenzoate at 98.5 conversion after 8.5 hours.

The ratio of F /F represents the efiiciency of utilization of radicalsfrom the initiator in question for the polymerization of vinyl monomers(styrene) compared to that of t-butyl peroxybenzoate. If the radicalsfrom the initiator were utilized as eifectively as those of t-butylExample IV.Polymerization of Vinyl Acetate The polymerization wasperformed in a sealed tube, under nitrogen, containing 2.5 g. of vinylacetate, 2.5 g. of benzene and the amount of peroxide shown below at C.for 1% hours. After this time, the tube was cooled and the amount ofpolymer formed determined by evaporating off the exces monomers andsolvent. The results are shown in Table IV below:

TAB LE 1V Percent poly(vinyl acetate) with 0.119 0. 0595 Peroxide 0i [0Z2,2-di-(t-butylperoxy)4-methylpentane 38. 3 27. 72,2-di-(t-butylperoxy)butane 31. 0 24. 4

Example V.Foaming and Curing of Elastomer The following formulation wasmixed and blended on a two roll rubber mill (parts are by weight):

Parts Ethylene propylene terpolymer (Nordel 1070) 100.0

Carbon black (SRF)-(filler) 80.0 Zinc oxide (accelerator) 5.0 Age RiteResin Dtrimethyldihydroquinoline (antioxidant) 1.0 Sulfur 0.332,2'-azobis(isobutyronitrile)(blowing agent) -2.02,2-di-(t'butylperoxy)-4-methylpentane 2.0

Samples 1" x 1" x 0.17" were foamed and cured in an oven at 300 F. for20 minutes or at 320 F. for 15 minutes. The results are shown in Table Vbelow:

TAB LE V Density of elastomer, Gram/co, Blowing agent, 300 F./20 320F./15 parts used minutes minutes The cured samples containing theblowing agent had a fine cellular structure while those without theblowing agent did not.

Example VI.Foaming and Curing The following formulations were mixed andblended on a two roll rubber mill:

Parts Ethylene-propylene terpolymer (Nordel 1070) 100.0

Carbon black (SRF) 80.0 Zinc Oxide 5.0 Age Rite Resin D 1.02,2-Azobis(isobutyronitrile) 2.0 Peroxide 0-2.0

These formulations were placed in a 5" x 5" x 0.075 mold at 320 F. Themold was closed under 12 tons of total pressure. After 15 minutes, themold was opened hot and the samples cooled to room temperature and theirdensities and ultimate tensile strength determined. The results aregiven below in Table VI:

TAB LE VI Ultimate tensile, Density Peroxide p.s.i. (g.)/cc.

None 66. 3 0. 86 2,2-di-(t-bntylperoxy)-4-methylpentane (A). 1, 998 1.07 n-Butyl 4,4-di-(t-butylp eroxy)-valerate (B). 1, 813 1. 25

1,1-di-(t-butylperoxy) -3,3,5-trimethylcyelohexane (C) 1, 343 1. 19

cal generators as polymerization initiators, the improvement whichcomprises employing as free radical generator, in the range of about0.01% to 5% by weight based on monomer weight, a peroxyketal of theformula R is selected from the group consisting of lower alkyl and CCR3;1'1.

the R s are selected from the group consisting of t-alkyl of 4-7carbons, t-cycloalkyl of 47 carbons, t-(ar)alkyl of 9-20 carbons and,taken together with participate in forming 1, 2, 4, 5-tetraoxacycloalkylof 7-13 carbons wherein an oxygen atom of each peroxy group is attachedto a tertiary carbon atom;

R and R are selected from the group consisting of H, lower alkyl,cycloalkyl, lower alkoxy, cycloalkoxy, phenoxy or substituted phenoxy,aralkoxy, acyloxy and aroyloxy, with the proviso that R and R can be thesame or different except that only one can be H;

R, is selected from the group consisting of H, lower alkyl,

cycloalkyl, lower alkoxy, cycloalkoxy, phenoxy or substituted phenoxy,aralkoxy, acyloxy and aroyloxy, with the proviso that R, is other than Hwhen R is methyl; and

R and R can be the same or different and are selected from the groupconsisting of H and lower alkyl.

2. The process of Claim 1 wherein said diperoxyketal is 2,2-di(t-butylperoxy -4-methylpentane;

2,2-di (t-amylperoxy) -4-methylpentane;

3,3-di (t-butylperoxy) heptane; or

4,4-di(t-butylperoxy)heptane.

3. The process of Claim 2 wherein said monomer is styrene.

4. The process of Claim 2 wherein said monomer is vinyl acetate.

References Cited UNITED STATES PATENTS 2,818,437 12/1957 Wildi et al.260-Dig. 28 3,296,184 1/1967 Portolani et al. 26088.2 S 3,470,119 9/1969Benning et al 2602.5 R 3,686,102 8/ 1972 Groepper et al. 260-2.5 HA

HARRY WONG, JR., Primary Examiner U.S. Cl. X.R.

2602.5 R, 2.5 H, 2.5 HA, 41 C, 67 UA, 77.5 UA, 78.4 R, C, 88.3 R, 88.7D, 89.5 A, 89.7 R, 91.1 M, 91.7, 92.1 R, 92.3, 92.8 R, 93.5 R, 94.2 R,94.9 R, 861, Digest 28

